Art of pyrolysis



Dec. 16, 1930. N. E. LooMls ET AL 1,785,274,

ART OF PYROLYSIS Filed May 5l, 1923 PUMP FEED

FURNAcl-l Patented Dec. 16, 1930 -A UNITED STATES Y'PATENT OFFICE NATHANIEL E. LOOIMIS, ALBERT H. TOMLINSON, .AND FRANK A.HOWARD, OIF ELIZA- Y BETHI, NEW JERSEY, ASSIGNORS TO STANDARD OIL DEV1311.01?MENTE'r COMPANY, A

CORPORATION 0F DELAWARE ART OF PYROLYSIS Application filed May 31,

sirable at all points is not always realized.

In accordance with the features of the present invention, a close control may be had for cracking in passages largely or wholly dependent upon the contained heat of the oil, in general, and in other aspects there 1s provided a conversion process in which the hydrocarbons are not only heated up to cracking temperature in a heated passageway but are cracked to an optimum extent, and' then are transferred to a digesting zone for a continuation of the cracking.

Referring'moreparticularly to the drawing,`the reference character Adesignates a heated conduit or passageway of suitable construction, for example a bank of tubes 1 connected at the ends by cross-over connections 2 from tube to tube and row to row to allow ow of fluid in a consecutive'path arid arranged in a furnace or otherwise heated. Joined to the first passageway A by a pipe 3 having a' check-valve 4 is a further passageway B of suitable construction.

' This may be for instance in the form of a larger passage or drum if desired, and in y any case is guarded against material heat loss, as by being covered with insulation or mounted so as to be bathed by hot gases, as preferred, in order to avoid heat loss. Another. drum B may be also employed 1f desired, connected so as to be operated elther .relay-wise or Asimultaneously with the drum B. it being understood that such duplication of drums is merely a matter of choice, depending upon circumstances. An outlet plpe 1923. Serial No. 642,400.'

7 leads on from the upper portion of the drum 0r heat-retaining passageway, preferably through a pressure-release valve 8 to any suitable vapor separator C. Condensers are also provided. When desired, a fractional condenser may be built inthe same shell above the vapor separator, and in the example illustrated comprises rectifying plates 9 and a collecting pan 10 for collecting heavier condensate 'for forwarding through a cooling coil 11 to a receiver (not shown). A vapor pipe 12-leads to a final condenser 13 and receiver (not shown).

Thermometers and pressure gauges are applied at points in the system as desired. y

A feed pump 14 serves to supply feed oil to the system, and the feed line 15 leads, fOr

example through a heat exchanger 16 in the path of the vapors, to the coil A by a pipe 17. Communication across from the feed line to the connection 3 is provided by a branch 18 from the feed line posterior to the heat exchanger and a branch 20 from the cold feed line anterior to the heat exchanger. From 4heating passageway section A and thence to the digesting passageway section B. As the temperature in the digesting passageway primarily follows that of the heating passageway, if the coil or heating passageway be run at an optimum temperature so far as the operation to be performed therein is concer-ned, it will often occur that the drum or digesting passageway will tend to 'run at a temperature higher than desirable for the optimum eiciency of such part of the process.` In accordance with the present invention the digesting passageway temperature may be maintained at any desired point below the coil temperature. `When the temperature in the digesting passageway shows a tendency to run too high, the valve 19. may be opened up as necessary and the temperatureA is moderated as required by introduction of the relatively cooler oil from the branch 18. If still cooler oil is desired, the Valve 21 may be opened up as necessary. Thus by drawing on one or the other or both feed line branches as preferred and vintroducing the relatively cooler fluid the temperature in the digesting passageway may be controlled as desired. 7hile two branches, tapping the feed line anterior to and posterior to the heat exchanger are advantageous, it will be understood that the invention contemplates in its simplest form one .such branch from the feed line irrespective of the presence or absence of a heat exchanger. Meters M may be placed in the branches to permit measurement of such feed. lVhile the introduction of feed stock into the second or digesting section of a conversion system as described makes possible a temperature control of the digesting zone separately from that Yof the first portion of the converslon system, it at the same time allows the utilization of excess heat brought from the first zone to convert additional quantities of stock which may be introduced into the second zone and correspondingly produces an efficient throughput. f

`As an example of some temperatures obtainable in a system according to the foregoing:

Operating at a pressure of 350 lbs. per square inch, (this being the pressure in B), on' a mid-continent gas oil of 34 B., the coil outlet showed 890 F. Vith this, the temu perature of the products leaving the passageway-B was around 820 F. By suitably opening up on the direct feed line branch 18 to the passageway B however, the temperature was controlled to 7 60 F.

In operating according to the desired detail of our process, the hydrocarbon material to be converted is passed through the heating zone A at a rate, temperature and pressure to secure optimum conditions :for cracking therein. A conversion in the coil or heating zone may be readily secured if desired to tthe extent of more than half of the total amount for the system, for instance. Preferably, although not necessarily, the temperature-pressure condition will be such that the hydrocarbons as subjected to conversion in the coil or heating passageway Will be substantially completely in vaporous form. From the actively heated zone these hydrocarbons largely in the :form of vapors then proceed to the succeeding passageway or zone guarded against heat loss externally, where the conversion process or digestion continues. By admitting relatively cooler stock also to the digesting zne the temperal ture may be held down here as desired and such additional stock subjected to conversion. The temperatureof the digesting zone is preferably regulated, as described, so as to canse condensation of a substantial proportion of the vapors coming from the heating passageway. Under these conditions the latent heat of vaporization of these condensed bodies is made use of for the heating and conversion of the relatively cooler stock admitted directly to the digesting zone. The optimum temperature for thedigestion zone depends upon the character of the hydrocarbons fed to the system and on the pressure. In general the preferred temperature is that which will maintain in the liquid phase those hydrocarbons in the mixture boiling above 450 F. and permit vaporization of the hydrocarbons boiling below 450C F. (at atmospheric pressure). Under these conditions the converted products leaving the digesting zone will consist of a mixture of vaporized light hydrocarbons and fixed gas with heavier hydrocarbons in the liquid phase. It will be understood that there will exist a small proportion of the light hydrocarbons in solution in the liquid phase in the heavier hydrocarbons, and a small proportion of heavier hydrocarbons in the vapor phase, this overlap being a necessary incident of the character of the mixture.

From the digesting zone the products all proceed preferably through a pressure release valve to the vapor separator, where vapors are separated and pass up to the condenser-s, higher boiling constituents condensing out first and being collected by the pan l0, while lighter products pass on to the'iinal condenser. Ordinarily the digesting zone or zones will be full of liquid oil up to the level of the outlet pipe 7 Under these conditions all fluid products (vapors and liquids, with or without suspended solids) pass Ftogether through that pipe to the vapor separator. pUnder seine conditions, however, vapor alone or liquid alone may be withdrawn. Residunm may be taken off from the bottom of the vapor scparator by the pipe 25.

By opening up the valve 23 and closing the valve 2l the 'hot products from the coil A may ,be by-passed direct to the vapor separator.

This is advantageous in particular in emergen cies. lV ith valves 23 and 24: both open the digesting passageway may be drained out into the vapor separator. A pump may be placed in the line 22 if desired.

For introducing the cooler hydrocarbon feed into the second zone or digesting passageway, if preferred instead of tapping'off a branch from the feed line, an additional line from a separate feed source may be provided. l

lVhile the supplemental feed or temperature control feature is particularly advantageous in operating by heating and cracking to an optimum extent and largely or Wholly in the vapor phase in a heated passageway and then passing the hydrocarbons to a further digesting passageway', the described procedure is of some merit, for regulative purpose at least, wherever hydrocarbons are heated in one zone and allowed to digest in another zone, irrespective of how much or how little cracking, or vaporization is accomplished in the heating zone.

Although we have described our invention by reference to certain specific details, it will be understood that this is for the purpose of illustration, and that changes may be made which come within the 4spirit and scope of the invention.

l/Vhat we claim is:

1. In apparatus of the character described, the combination of a coil, means for heating said coil, an enlarged digesting passageway having provision against material temperature loss, a connecting pipe between said coil and the enlarged digesting passageway, a check-valve in -said connecting pipe, a vapor separator, a connecting pipe betweenthe upper portion of said enlarged digesting passageway and the vapor separator, a pressure release valve in the last named connecting pipe, a feed pipe connecting through a heat exchanger to the coil first `mentioned, branch pipes from the feed pipe anterior and posterior to the heat exchanger and connecting rey spectively to the digesting passageway, and

a by-pass pipe leading from the coil around the digesting passageway to the vapor separator.

2. In apparatus of the character described, the combination of a heating conduit, a digestingv passageway connecting therewith and having provision against material telnperature loss, a check-valve between said conduit and said digesting passageway, a vapor separator connecting with the upper portion of the di esting passageway, a feed pipe connecting t rough a heat-exchanger to the conduit first mentioned, branch pipes from the feed pipe anterior and posterior to theheat exchanger and connecting respectively to the digesting passageway, and a by-pass pipe leading from the conduit around the digesting passageway to the vapor separator.

3. In apparatus of the character described, the combination of a heating conduit, a digesting passageway connecting therewith and having provision against material temperature los-s, a check-valve between said conl duit and said digesting passageway, a feed pipe connecting through a heat exchanger to the conduit first mentioned, branch pipes from the feed pipe anterior and posterior to the heat exchanger and connecting respectively to the digesting passageway, and a bypass pipe leading from theconduit around the digesting passageway.

4. In apparatus of the character described, the combination of a heating conduit, a digesting passageway connected therewith and having provision` against material temperature loss, a check-valve between said condult and said digesting passageway, a Afeed pipe vconnecting to the. conduit first mentioned, a

leading from the conduit around the digesting passageway.

5. In apparatus of the character described, the combination of a heating conduit, a digesting passageway connected therewith and aving provision against material temperature loss, a check-valve between said conduit and said digesting passageway, a feed pipe connecting to the conduit first mentioned, means for supplying relatively cool oil to the digesting passageway as desired, a rectifying tower and a by-pass pipe from 'said heating conduit around the digesting passageway and leading directly to the rectifying tower. 6. The improvement in the art of pyrolytic conversion under pressure of hydrocarbon oils to lower boiling products, which comprises flowing a stream of the hydrocarbons through a heating Zone under conditions of temperature, pressure, and time such as to give substantial cracking and substantial vaporization, then through a zone in which the oil is held for a relatively longer time, introducing relatively cool oil into the last mentioned zone to hold a temperature therein substantially lower than the temperature in the first zone but not below an effective cracking temperature, and withdrawing substantially all the fluid products together from the last mentioned zone.

7. The improvement in the art of pyrolytic conversion of hydrocarbons to lower boiling products, which comprises heating a stream of the hydrocarbons in a heating zone and effecting substantial cracking therein, then allowing further cracking in a chamber separate from the Zone in which the aforesaid heating occurred, while controlling the temperature in the said chamber by introducing therein a relatively cool hydrocarbon oil, and withdrawing substantially all the iiuidiproduets together from the upper portion of said chamber.

8. The improvement in the art of pyrolytic conversion of hydrocarbons to lower boiling products, which comprises heating the hydrocarbons and effecting substantial cracking, allowing cracking to continue in a digestion zone solely on the acquired heat, while controlling the temperature by introducing fluid hydrocarbons cooler thanthe heated hydrocarbons, and withdrawing substantially all the fluid products together from the digestion zone.

NATHANIEL E.' LOOMIS. A ALBERT H. TOMLINSON.

FRANK A. HOVARD.

DISCLAIMER 1,785,274r-Nathanel E. Loomis, Albert H. Tomlinson, and'Franc A. Ioward, Elizabeth, N. J. ART 0F PYRoLYsIs. Patent dated December 16, 1930. Disclaimer filed July 15, 1933, by the assignee, Standard Oil Development Company. Hereby enters this disclaimer, namely, to any construction of claim 7 of said patent except that which requires the relatively cool hydrocarbon oil to be an oil which has not been heated at all or which has been heated only by heat exchange with vapors evolved from the oil which has undergone cracking, and to any construction of claim 8 of said patent except that which requires the fluid hydrocarbons cooler than the heated hydrocarbons to be fluid hydrocarbons which have not been heated at all or which have been heated only by heat exchange with vapors evolved from the oil which has undergone cracking. i v

[Oficial Gazette `.August 8., 1.933.] 

